A higher octane gasoline ignites harder so it prevents pre-ignition and spark knock at higher compression ratios. That gasoline does not produce more horsepower. It allows engine builders to design an engine that can produce more horsepower from that gas. To say it a different way, you need to use a higher octane gasoline when you have problems with spark knock. If spark knock is not a problem, all the higher octane ratings get you is a fuel that is harder to light off. If you have weak spark or worn spark plugs, a spark-related misfire is less likely to occur when running a lower octane fuel.
Gasoline formulations and additives vary a great deal in different areas of the country so it is impossible to say what you need for a specific engine. The best you can do is start with a mid-grade and see if spark knock is a problem. Based on that, you can move to a higher or lower octane gas. The goal should be to use the lowest octane possible for lowest cost and most complete combustion.
Another way to look at it is if higher octane really produced more horsepower, everyone would use it. Engines do not run on octane to produce power; they run on gasoline.
Saturday, July 30th, 2016 AT 2:29 PM